Sugar purification



United States Patent Ofice 3,479,221 Patented Nov. 18, 1969 3,479,221 SUGAR PURIFICATION Frank C. Buhl, Birmingham, Mich., and Ronald D. Lees and Daniel J. Monagle, Wilmington, Del., assignors to Hercules Incorporated, Wilmington, Del., a corporation of Delaware No Drawing. Filed Nov. 15, 1966, Ser. No. 594,357 Int. Cl. C13d 3/00, 3/14 US. Cl. 12746 13 Claims ABSTRACT OF THE DISCLOSURE Process of purifying an aqueous sugar slurry employing an acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer as an aid in flocculating and settling suspended solids.

The present invention relates to sugar manufacture and more particularly to the use of flocculants as processing aids in the manufacture of sugar.

Sugar beets and sugar cane are the two major raw materials from which sugar is obtained. There is not much difference between a typical conventional process of manufacturing sugar from beets and one of manufacturing sugar from cane. These processes will now be described very briefiy to aid in understanding the present invention.

After the raw whole sugar beets are washed and shredded they are passed through a diffuser countercurrent to a flow of water which dissolves out substantially all of the sugar and leaves behind the beet pulp for drying as livestock feed. The efiluent from the diffusion process includes water containing about 15% dissolved sugar as well as both dissolved and undissolved impurities. By means of at least one step each of screening, liming and carbonating much of these impurities are removed. Additional impurities are removed by allowing the aqueous sugar solution to settle. The eflluent (supernatant) from the settling (clarification) step contains in solution substantially all of the original sugar in a relatively pure form. The final pure white sugar product is obtained from the settling step efl'luent by further processing this efiluent in accordance with conventional steps such as evaporating, crystallizing, centrifuging, drying and grinding. The material which settles during the settling step is vacuum filtered, the filtrate (sweet water) being recirculated to the liming steps. Either the lime is recovered from the filter cake of the vacuum filtration step and reused in the process, or this filter cake is simply discarded.

Raw sugar cane is cut to a fibrous pulp and slurried in hot water to dissolve the sugar from the pulp. Impurities (pulp, dirt, etc.), are removed from the slurry by settling. The efiluent (supernatant) from the settling (clarification) step is processed to the final sugar product by subjecting this effluent to conventional steps such as evaporating, crystallizing, centrifuging, drying and grinding. The material which settles from this slurry is vacuum filtered, the filtrate (sweet water) being recirculated to the process and the filter cake being discarded.

The present invention is useful in the manufacture of sugar from cane and beets in either the settling step or in the filtration step, or in both steps.

Although the process steps employed in the manufacture of sugar from cane and beets are very similar, the impurities encountered in the two processes are quite different. The impurities in beets are primarily organic whereas those in cane are primarily inorganic. In addition, the amount of impurities in cane is considerably greater than in beets. In view of this it cannot be predicted that merely because a given flocculant processing aid is useful in the manufacture of sugar from cane it will also be useful in the manufacture of sugar from beets, or vice versa.

The sugar industry, both cane and beet, has been striving for increasing product yields as well as for decreasing stream pollution.

In accordance with the present invention it has been found that these objectives of the sugar industry are accomplished to a surprisingly high degree by contacting an aqueous slurry containing sugar and impurities (either from cane or beet) just prior to the settling or vacuum filtration steps with a small amount of a certain acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate (acrylamide-MTMMS) copolymer. The use of said copolymer in the settling (clarification) step results in the copolymer flocculating the sugar impurities into large dense fiocs which increases the settling rate of the impurities and the amount thereof settled. The use of said copolymer in the vacuum filtration step results in the copolymer flocculating the sugar impurities into large dense flocs which causes the fiocculated particles to release their bound water (to dehydrate) far more readily during vacuum filtration.

The eifectiveness has been determined of the particular copolymer of the present invention to facilitate the settling (clarification) step and the vacuum filtration step in the manufacture of sugar from both cane and beets.

The following examples illustrate various embodiments of the present invention. These examples are not intended to limit the present invention beyond the scope of the appended claims. In these examples and elsewhere herein parts and percent are by weight unless otherwise indicated.

' EXAMPLES 1-11 Cane sugar'Settling (during clarification) qualitative These examples were carried out to determine the effect of various polymeric flocculating agents on the settling characteristics of suspended solids impurities in cane .sugar aqueous slurries.

TABLE 1.CANE SUGARFSETTI E IE' IC IJJJEURIN G CLARIFICATION) QUALI- [Effect of Various Flocculating Agents on Settling Characteristics of Suspended Solids Impurities in Cane Sugar Aqueous Slurries] Floceulating Agent Visual Observation Ex. No. Name a Amount b After Standing 5 Mins.

Very slow settling. None {Turbid supernatant. 50 {Very slow settling.

Turbid supernatant.

2 Commercial Flocculating Agcnt 3 ..do l 00 Slow settling.

' Turbid supernatant.

Medium floc size. Slow settling. Turbid supernatant. Fine fioe size.

Slow settling. Turbid supernatant.

5 94% Acrylamide, 6% MTMMS 0 Medium floe size. 6 d0 0. 50 Fast settling.

Clear supernatant. {Medium fioc size.

a Examples 2-4 used an acrylamide-based anionic flocculating agent available commercially as Separan AP-30.

b P.p.m. dry weight basis by weight of total slurry treated, added as a 0.01% aqueous solution.

EXAMPLES 12-27 Beet sugarSettling (during clarification) qualitative These examples were carried out to determine the eifect of various polymeric flocculating agents on the settling characteristics of suspended solids impurities in beet sugar aqueous slurries.

placed in each of several l-liter graduated cylinders. Flocculating agent was mixed With each portion by adding the flocculating agent thereto and pouring 5 times back and forth from filled to empty graduated cylinders. The resulting mixtures were allowed to stand 5 minutes and the settling characteristics of the suspended solids impurities One-liter portions of beet sugar juice slurry (effluent after completion of the liming-carbonation steps) were were observed.

Further details appear in Table 2 hereinafter.

TABLE 2.BEEI SUGAR-SET'ILING (DURING CLARIFICATION) QUALITATIVE [Eifect of Various Flotlzculating Agents on Settling Characteristics of Suspended Solids mpurities in Beet Sugar Aqueous Slurries] Floceulating Agent No. Name 12 None- Visual Observations Amount b After Standing 5 Mins.

ery slow settling. None gurbid supernatant.

13 Commercial Flocculating Agent. 0.075 {g gg ggg ii' Very fast settling. 14 1o {Hazy supernatant with many fines. 15 do 0 {Very fast settling.

- Clear supernatant with many fines.

Very fast settling. l6 do 1. 00 Iglear supernatant with only few nes. Very fast settling. 17 50 {Clear fsupentialtant without fines.

ery as se mg. 18 50 {Clear supernatant without fines. 19 94% Acrylamide, 6% MTMMS o. 05 g{ g%g Very fast settling. 2O 075 lgazyfsuperfiatant.

ery ast se ing. 21 10 {Clear supernatant with many fines.

Very fast settling. 22 .do 0. 25 Very jglear supernatant with only w nes. Extremely large floc. 23 ..do 0.75 Very fast settling.

[Very clear supernatant without fines.

25 8 3% Acrylamide, 17% MTMMS- Very fast settling. Very clear supernatant without fines. 0 05 {Very fast settling.

' Clear supernatant with many fines. 0 075 {Extremely large floc.

Extremely large flee. 2. 50

Very fast settling. Very clear supernatant without fines. Extremely large tloc. 2. 50 Very fast settling.

Very clear supernatant without fines.

P.p.m. dry weight basis by weight of total slurry treated added as a 0.01% aqueous solution.

5 EXAMPLES 28-35 Cane sugar-Settling (during clarification) quantitative These examples were carried out to determine the effect of various polymeric fiocculating agents on the settling EXAMPLES 57-61 Cane sugar-Settling (mud to be filtered) quantitative These examples were carried out to determine the eifect of various polymeric fiocculating agents on the settling rate of suspended solids impurities in cane sugar aqueous 5 rate of suspended solids impurities in cane sugar mud slurries. (Wet solids settled from the settling, i.e., clarification, One-liter portions of cane sugar juice slurry (formed by step). This mud is very wet (very concentrated slurry) cutting raw sugar cane to a fibrous pulp and slurrying and is vacuum filtered. As mentioned hereinbefore the in hot water) were placed in each of several l-liter gradul filtrate from this mud contains dissolved sugar (sweet ated cylinders. Flocculating agent was mixed with each water) and is recirculated to the process and the filter portion by adding the fiocculating agent thereto and pourcake is discarded. ing times back and forth from filled to empty graduated Two hundred fifty (250) ml. portions of cane sugar cylinders. The resulting mixtures were allowed to stand 3 mud were placed in each of several 500 ml. graduated minutes and the settling rate of the suspended solids imcylinders. Flocculating agent was mixed with each porpurities was determined by measuring the amount of tion by adding fiocculating agent thereto and inverting the supernatant which formed during this time. cylinders 5 times. The resulting mixtures were allowed Further details appear in Table 3 hereinafter. to stand 5 minutes and the settling rate of the suspended TABLE 3.-CANE SUGARSETTLING (DURING sollds lmpurltls dflermlnfid- CLARIFICATION) QUANTITATIVE Further details appear 1n Table 5 hereinafter. [Effect of Various Flocculating Agents on Settling Rate of Suspended Solids Impurities in Cane Sugar Aqueous Slurries] TABLE 5 CANE SUGAR SETTLING (MUD To BE Flocculating Agent Mllifsuusernagant [Eff fv FFILTE RED) QUANTITATIVE EX ter tan ing ecto arious locculatingA entsonthe Settlin Rate 1 S No Name Amount b 3 Mins. Solids Impurities in Cane Sugar Mud 0 uspended one None None Flocculatm A ent M] 5 Commercial Flocculating Agent. 0. 50 660 Ex. g g Aftcii' s ta r i ir i 00 70 No. Name Amount b 5 Mills. 31 83% Acrylamide, 17% MTMMS 0 50 800 32 0 s .00 820 57 None N n 2 33 60% A lamide, 0.25 580 58. Commercial Flocculating Agent. 4.0 500 34 do 0. 50 814 59. 94% Acrylamide, 6% MTMMS 4, 0 515 35 -do 2.00 835 30 60- 83% Acrylamide, 17% MTMMS 4,0 540 t 61 60% Acrylamide, MTMMS 4. 0 570 5 Examples 29 and 30 used an acrylamide-based anionic fiocculating agent available commercially aSSeparan AP-30. Example 58 used an acrylamide-based anionic fiocculating agent b P.p.m. dry weight basis by weight of total slurry treated, added as a available commercially as Separau AP-30. aqueous Solution, ad zildpm. weight basis1 by weight of total dry solids in mud treated.

e as a aqueous SO 11 1011. EXAMPLES 36-56 35 Beet sugar-Settling (during clarification) quantitative EXAMPLES 62-72 These examples were carried out to determine the eifect B t sugar sefl;ling d to b filt d) quantitative of various polymeric fiocculating agents on the settling rate of suspended solids impurities in beet sugar aqueous 4O f examples camedput to determine the efliect slurries of varlous polymeric fiocculating agents on the settling One-liter portions of beet sugar juice slurry (effluent at; figs z g i sghds g m Sugar B after completion of the liming-carbonation steps) were Ste Thi om t 111g, fi atlon, placed in each of several l-liter graduated cylinders. Floc- Vacs u A (very g i fi Slurry) culating agent was mixed with each portion by adding the r filtrate z l i I erembefore the fiocculating agent thereto and pouring 5 times back and Water) and i g il Ved Sugar (Sweet forth from filled to empty graduated cylinders. The recake is di i i q i e prgcess and filter sulting mixtures were allowed to stand 1 minute and the lime zfg 61 er 6 Ore or a ter recovfirlng the settlin rate of the sus ended solids im urities was determinged p P Two hundred fifty (250) ml. portions of beet sugar Further details appear in Table 4 hereinafter. were placed i each of seveial q' graduaied TABLE 4 BEET SUGAR SETTLING (D URING cylinders. Flocculatrng agent was mixed with each portion CLARIFICATION) QUANTITATIVE ganydaddigigtilocculltlmg agelnt thereto and lnverting the cyl- [Efiectofvarious Floceulating Agents onthe Settling Rate of Suspended ers {mes' e resu tmg .mlxtures were allowed to Solids Impurities in Beet Sugar Aqueous Slurries] stand minutes and the settling rate of the suspended r Floceulatiug Agent Ml. Supernatant 05 sohds lmpuntlqs determm.ed' Ex, After Standing Further details appear In Table 6 hereinafter. No. Name 8 Amount b 1 Min.

36 None 1 TABLE 6BEET SUGAR SETTLING M 37 Commercial Flocculatin Agent. 0.075 90 UD TO BE 38 do 0,10 1 FILTERED) Q ANTITATIVE 39 .do. 0. 25 150 Efiect of Various Flocculating Agents on the Settlin Rat S 40. do 0. 50 189 Solids Impurities in Beet Sugar Miid] e D uspended 41 do 0. 73 12 42 d0 1. 0 1 Flocculating Agent Ml. Supernatant i1; d0-

A t b After Standing 45IIIIII'i% 0501 132 62 5 46 75 a N 0.10 132 5 8 Nglig 0. 25 152 64- 10. 0 400 49 .do- 2. 00 190 65- 1 84 50 83% Acrylamide, 17% MTMMS 0.05 132 66 1 0 195 51 do 0. 10 5 67- 2. 0 24 52 do 0.50 157 68. .do 10, 0 5 0 53 do 2. 50 21 69- 3% Acrylamide, 17% MTMMSs 1, 0 355 54 60% Aerylamide, 40% MTMMS 0.075 7 70. o 10.0 560 55 do 0. 10 158 71- 60% Acrylamide, 40% MTMMS 1, 0 395 56 "do 0. 50 171 72. .do 10. 0 590 :1 Examples 63 and 64 used an acrylamide-based anionic fiocculating agent available commercially as Separan AP-30.

b P.p.m. dry weight basis by weight of total dry solids in mud treated, added as a 0.1% aqueous solution.

7 EXAMPLES 73-79 Cane sugarFiltration (mud) quantitative These examples were carried out to determine the eifect of various flocculating agents on the filtration rate of suspended solids impurities in cane sugar mud aqueous slurries.

Two hundred fifty (250) ml. portions of cane sugar mud were placed in each of several SOO-ml. graduated cylinders. Flocculating agent was mixed with each portion by adding flocculating agent thereto and inverting the cylinders times. The resulting slurries were poured into Buchner funnels lined with a No. 4 Whatman filter paper. A.22-inch mercury vacuum was applied to the funnels and the filtrates collected in 250-ml. graduated cylinders.

Further details appear in Table 7 hereinafter.

TABLE 7.CANE SUGAR-FILTRATION (MUD) QUANTITATIVE [Effect of Various Flooeulating Agents on Filtration Rate of Suspended Solids Impurities in Cane Sugar Mud] n Examples 74 and 75 used an acrylamide-based anionic flocculating agent available commercially as Separan AP-30.

b P.p.m. dry weight basis by weight of total dry solids in mud treated, added as a 0.1% aqueous solution.

EXAMPLES 80-93 Beet sugar-Filtration (mud) quantitative These examples were carried out to determine the effect of various flocculating agents on the filtration rate of suspended solids impurities in beet sugar mud.

Two hundred fifty (250) ml. portions of beet sugar mud were placed in each of several SOO-ml. graduated cylinders. Flocculating agent was mixed with each portion by adding flocculating agent thereto and inverting the slurries 5 times. The resulting slurries were poured into Buchner funnels lined with No. 4 Whatman filter paper. A 22-inch mercury vacuum was applied to the funnels and the filtrates collected in 250-ml. graduated cylinders.

Further details appear in Table 8 hereinafter.

TABLE 8.BEET SUGARFILTRATION (MUD) QUANTITATIVE [Effect of VariousSFlocculating Agents on Filtration Rate of Suspended olids Impurities in Beet Sugar Mud] Flocculating Agent Ex. Ml. Filtrate No. Name 8 Amount 11 After 5 Mins.

80 None None 81-- Commercial Flocculating Agent..- 10 18 82. .d0 20 29 83. .do 40 90 84-- 4% Acrylamide, 6% MTMMS 5 2g..- 0 10 41 8 Examples 81-83 used an acrylamide-based anionic flocculating agent available commercially as f Separan AP-30.

b P.p.m. dry weight basis by weight of total dry solids in mud treated, added as a 0.1% aqueous solution.

EXAMPLES 941 01 Cane sugar-Filter leaf tests (mud to be filtered) qualitative These examples were carried out to determine the efiect of various polymeric flocculating agents on the pickup characteristics of cane sugar mud.

One hundred (100) ml. portions of cane sugar mud were placed in each of several clean glass beakers. Flocculating agent was added to and mixed with each portion by pouring 8 times back and forth from filled beaker to empty beaker. A conventional filter leaf with filter cloth attached (this is conventional testing equipment in this art) was inverted into the cane sugar mud and held for 2 minutes. The filter leaf was then removed from the beaker and held upright for a drying time of 2 minutes. A 22- inch mercury vacuum was applied to the filter leaf throughout the tests.

Further details appear in Table 9 hereinafter.

TABLE 9.CANE SUGARFILTER LEAF TESTS (MUD TO BE FILTERED) QUALITATIVE [Effect of Various Flocculatiug Agents on the Pickup" Characteristics of Cane Sugar Mud] Dry, extremely thick.

Examples and 96 used an acrylamide-based anionic floceulating agent available commercially as Separan AP-30.

b P.p.m. dry weight basis by weight of total dry solids in mud treated, added as a 01% aqueous solution.

EXAMPLES 102-122 Beet sugar-Filter leaf tests (mud to be filtered) qualitative These examples were carried out to determine the effect of various polymeric flocculating agents on the pickup characteristics of beet sugar mud.

One hundred ml. portions of beet sugar mud were placed in each of several clean glass beakers. Flocculating agent was added to and mixed with each portion by pouring 8 times back and forth from filled beaker to empty beaker. A conventional filter leaf with filter cloth attached was inverted into the beet sugar mud and held for 2 minutes. The filter leaf was then removed from the beaker and held upright for a drying time of 2 minutes. A 22-inch mercury vacuum was applied to the filter leaf throughout the tests.

Further details appear in Table 10 hereinafter.

TABLE 10. CANE SUGAR-FILTER LEAF TESTS (MUD TO BE FILTERED) QUALITATIVE [Effect of Various Floceulating Agents on the Pickup Characteristics of Beet Sugar Mud] Floeculating Agent Visual Observations of Filter Cake Wet, extremely thin.

Dc. Wet, medium thin.

et thick.

Ex. No. Name a Amount b Slightly wet, very thick.

Dry, medium thick.

Dry, very thick.

et, thin.

Wet, medium thin.

Wet, thick.

Slightly wet, very thick.

Dry, very thick.

Dry, extremely thick.

1 Wet, medium thick.

2 Wet, thick.

4 Wet, very thick.

Dry, thick. Dry, very thick.

Examples 103-108 used an acrylamide-based anionic flocculating agent available commercially as Separan AP-30.

b P.p.m. dry weight basis by weight of total dry solids in mud treated, added as a 0.1% aqueous solution.

From the foregoing examples it will be readily apparent that the particular copolymer fiocculating agent of the present invention, as compared with typical flocculant agents of the prior art, gives substantially better performance (even at lower concentrations) from the standpoint of flocculation, settling, and filtration. The amount of the particular copolymer fiocculating agent applicable in the present invention is not critical and may vary considerably. In the settling (clarification) step the amount of copolymer flocculating agent of the present invention usually will be about 0.01-l%, preferably 0.0%5%, dry weight basis by weight of the total aqueous sugar slurry treated. The amount of copolymer flocculating agent of the present invention in the filtration step usually will be about 0.l%-100%, preferably about 1%-40%, dry weight basis by weight of the dry solids in the aqueous sugar slurry treated. Those skilled in the art to which the present invention relates will appreciate that aqueous sugar slurries and muds vary considerably and that the amount of any given flocculating agent employed will vary accordingly. The foregoing examples were carried out on on the same aqueous sugar slurries and muds.

The copolymer flocculatin'g agent of the present invention consists by weight thereof essentially of 99%20% acrylamide and 1%80% MTMMS, preferably 97%-50% acrylamide and 3%50% MTMMS, 95 %60% acrylamide and 5%40% MTMMS being specifically preferred.

Preparation of the particular copolymer employed in the present invention is not claimed herein nor is it per se a part of the present invention. However, the preparation of said copolymer is quite important. In fact, applicants know of only one process which will produce a product having the properties of the particular copolymer applicable in the present invention. For the sake of completeness this process will now be disclosed. It may be referred to as precipitation polymerization.

The precipitation process broadly comprises polymerizing a solution of acrylamide and MTMMS monomers in aqueous tertiary butanol, aqueous acetone or aqueous tertiary butanol-acetone in the substantial absence of air while agitating the solution to give a copolymer product that can be isolated by filtration, the aqueous tertiary butanol and aqueous acetone being solvents for the monomers but nonsolvents for the copolymer product.

Several of the conditions of this precipitation polymerization process are critical, and these conditions will now be discussed.

The solvent for the monomers must be aqueous tertiary butanol, aqueous acetone or aqueous tertiary 'butanol-acetone (i.e., mixtures of water with tertiary butanol or acetone alone or with both). The concentrations of water in said mixtures must be 30%65%, preferably 45%- 60%, by weight of said mixtures.

The polymerization reaction temperature must be 0 C.60 C., preferably 0 C.40 C.

The polymerization may be carried out either in the presence or absence of a polymerization catalyst (initiator), but preferably a polymerization initiator will be used. Both the types and amounts of free radical initiator applicable are well known in this art. Peroxygen compounds are quite suitable; including, e.g., ammonium persulfate, potassium persulfate and hydrogen peroxide. Other free radical initiators include, e.g., a,a-azo-bis-iso'butyronitrile. The peroxygen initiators may be used alone or in combination with activators (also well known in this art) including, e.g., sodium bisulfite, sodium thiosulfate, tetramethylenediamine, thiourea and ferrous chloride, said combination forming a redox system. The amount of initiator usually will not exceed 0.5%, preferably is 0.05% 0.02%, 0.05% being specifically preferred, by weight of the combined weight of monomers.

Although not necessary, preferably the precipitation polymerization is carried out in the presence of a salt dissolved in the polymerization reaction mixture. By polymerizing in the presence of a salt, or a buffer system comprising one or more salts in combination with another material to complete the buffer system, recovery of the copolymer product is substantially facilitated. These salts and buffer systems include, e.g., (1) alkali metal and ammonium acetates, carbonates, bicarbonates, chlorides, phosphates, sulfates, bisulfates, borates; (2) buffer systems comprising (a) mixtures of weak acid or weak base and their salts including (b) phthalates, citrates, borates, phosphates, acetates, ammonium hydroxide, ammonium acetate, ammonium chloride, (c) specific combinations including mixtures of boric acid-borax, citric acid-sodium acid phosphate, sodium carbonate-sodium bicarbonate, ammonium chloride-ammonium hydroxide, ammonium acetate-ammonium hydroxide; or (3) any combination of (1), and (2).

The amount of salt which may be used is about 0.1%- 2.0%, preferably about 0.2%-0.7%, by weight of the reaction mixture. If the amount of salt exceeds about 2.0%, usually there is a tendency for the granules of the polymeric product to agglomerate in the polymerization reaction mixture. The manner of adding the salt and the point at which it is added are not critical.

The following is a specific example wherein the precipitation process was used in preparing the particular copolymer applicable in the present invention.

To a glass reactor were charged 116 parts of distilled water, 104 parts of acrylamide, 129 parts of tertiary butanol, 3.9 parts of Tergitol NP14 (nonylphenyl polyethylene glycol ether), 92.4 parts of a 23% aqueous so lution of MTMMS, and 0.05 part of potassium persulfate. The pH was adjusted to 5.3 by addition of NH OH. The solution was heated to 45 C. The atmosphere and dissolved air were replaced with nitrogen by a series of evacuations and repressurizations. The pressure was then adjusted to 148 mm. to maintain reflux at 45 C. Then 6.26 parts of a 1% aqueous solution of tetramethylethylenediamine was added at a uniform rate during 1.5 hours. Refiuxing the reaction mixture was continued for an additional 1.5 hours. Polymerization occurred and the copolymer precipitated during this 3-hour period. The copolymer was washed with acetone and dried in a vacuum oven at 50 C. There was obtained 130 parts of copolymer containing 93.5% solids. It contained 19 weight percent MTMMS and 81 weight percent acrylamide (dry basis).

Although the fiocculating agent in accordance with the present invention may be added in dry form to the sugar juice slurry being treated, it is preferred to add it as an aqueous solution in order to get faster and more complete dispersion thereof throughout said slurry.

As many apparent and widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

What we claim and desire to protect by Letters Patent is:

1. Process of purifying an aqueous sugar slurry which comprises contacting said slurry with an acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer, allowing the resulting slurry to settle, thereby (1) increasing the rate at which suspended solids flocculate and settle out of said slurry, and (2) increasing the amount of suspended solids which flocculate and settle out of said slurry.

2. Process of purifying an aqueous sugar slurry which comprises stirring a mixture of said slurry and about 0.01-10 p.p.m., dry weight basis by weight of the total sugar slurry treated, of an acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer, thereby (1) increasing the rate at which suspended solids flocculate and settle out of said slurry, and (2) increasing the amount of suspended solids which flocculate and settle out of said slurry.

3. Process of claim 1 wherein the amount of said acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer employed is about 0.05-5 p.p.m., dry weight basis by weight of the total sugar slurry treated.

4. Process of claim 1 wherein the copolymer consists by weight thereof essentially of 99%20% acrylamide and 1%80% beta methacrylyloxyethyltrimethylammonium =rnethyl sulfate.

5. Process of claim 1 wherein the copolymer consists by weight thereof essentially of 97%50% acrylamide and 3%50% beta methacrylyloxyethyltrimethylammonium methyl sulfate.

6. Process of claim 1 wherein the copolymer consists by weight thereof essentially of 95 %60% acrylamide and 5%40% beta methacrylyloxyethyltrimethylammonium methyl sulfate.

7. Process of purifying an aqueous sugar slurry which comprises contacting said slurry with an acrylarnide-beta methacrylyloxyethy]trimethylammonium methyl sulfate copolymer, and then dewatering said resulting slurry.

8. Process of purifying an aqueous sugar slurry which comprises stirring a mixture of said slurry and 01-100 p.p.m., dry weight basis by weight of the solids in said slurry, of an acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer, and then dewatering said resulting slurry while continuing to stir same.

9. Process of claim 8 wherein the amount of said aciylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer employed is about 1-40 p.-p.m., dry weight basis by weight of the solids in said slurry.

10. Process of claim 8 wherein the copolymer consists by weight thereof essentially of 99%-20% acrylamide and 1%80% beta methacrylyloxyethyltrimethylammonium methyl sulfate.

11. Process of claim 8 wherein the copolymer consists by weight thereof essentially of 97%50%acrylamide and 3%50% beta methacrylyloxyethyltrimethylammonium methyl sulfate.

12. Process of claim 8 wherein the copolymer consists by weight thereof essentially of 95 %60% acrylamide and 5%40% beta methacrylyloxyethyltrimethylammonium methyl sulfate.

13. Process of purifying an aqueous sugar slurry which comprises contacting said slurry with an acrylamide-beta methacrylyloxyethyltrimethylammonium methyl sulfate copolymer, allowing the resulting slurry to settle, removing the resulting settled material (mud) from the supernatant thus formed, contacting said mud with an acrylamide-beta methacrylyloxyethyltrimethylam-monium methyl sulfate copolymer, and then dewatering said mud.

References Cited UNITED STATES PATENTS 2,937,143 5/1960 Goren 1275O 3,171,805 3/1965 Suen et al 21054 3,276,998 10/1966 Green 210-54 3,278,506 10/1966 Chamot et al 210-54 3,374,143 3/1968 Stephenson 21054 FOREIGN PATENTS 1,095,926 12/ 1954 France.

OTHER REFERENCES Food Additives, Modified Polyacrylamide Resin (Fed. Reg), abstract in chem. abstracts, vol. 64, p. 20513 (1966).

Clarification of Sugar Cane Juice With Polyelectrolytes, A. B. Bonneville, Sugar, November 1953, pp. 36-39.

MORRIS O. WOLK, Primary Examiner D. G. CONLIN, Assistant Examiner US. Cl. X.R. 12748; 210 s4 I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,479,221 November 18, 1969 Frank C. Buhl et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, TABLE 2, opposite Example 16, cancel Column 9, lines 21 and 22, "out on on the same" should read out on the same Signed and sealed this 2nd day of June 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, Commissioner of Patents Attesting Officer 

